Centrifugal electrical mercury switch



Feb. 4, 1936.

G. S. MOORE CENTRIFUGAL ELECTRICAL MERCURY SWITCH Filed Jan. 5, 1934 Agra W @M (Z? Z/MM @Wqm Patented Feb. 4, 1936 UNITED STATES PATENT OFFICE Guy '8. Moore, Salem, Mass., ass ignor of fifty-one per cent to Eugene B. Fraser, Lynn, Mass and twenty-four per cent to Fred H. Rowe, Gloucester, Mass.

Application January 5, 1934, Serial No; 705,407

4 Claims.

My present invention relates to electric switches and more particularly to an automatic electrical switch centrifugally operated by rotating bodies.

The present application is to be identified with my previous application filed May 9, 1933, Serial Number 670,095. The present invention is designed to operate centrifugally using mercury as a medium for contacting or opening and closing an electrical circuit. dinary cup shaped cavity might be satisfactory but where precision is necessary it has been found that a rotating cup is more or less unreliable with respect to quick action due to the fact that the cup starts rotating first while the ball of mercury, is more sluggish and the centrifugal effect produced on the mercury ball at the bottom of the cup is sometimes delayed causing electrical circuit to be opened a few seconds after the cup starts rotating and while this lapse of time if always constant might be compensated for otherwise it has also been found that such lapse of time is irregular and undependable; therefore The principal object of my invention is an improved centrifugally operated mercury switch for electrical contacts and the like;

Another object is an improved centrifugal mercury cup adapted to discharge the mercury upwardly from the lower gravity position which it normally resides in at rest immediately when the cup starts to rotate, and

Other objects and novel features comprising the construction and operation of my invention will appear as the description of the same progresses.

In the drawing illustrating the preferred embodiment of my invention,

Fig. 1 shows a typical and substantially vertical cross section of the revolving cup and drive shaft surrounded by a casing and a dotted line circuit for an incandescent lamp illustrating one of its uses, and

Fig. 2 is a cross section taken on the line 22 of Fig. 1 and showing the complete symmetrical cross sections thereof.

Referring more in detail to the drawing ID indicates a rotatable shaft link preferably composed of fibre having male and female end portions II and I2 -respectively to which may be connected driver or driven shafts l3 and I4 either of a rigid or flexible nature. solidly attached to shaft link 10 is a cup member I5. The cup member I5 is preferably made of some insulating material such a's bakelite, hard'rubber or the like and may beif desired moulded to the Under some conditions an orlink I or if desired it may attached by any other means. Cup member I is provided with a cup shaped cavity l6 adjacent its top portion being closed on all sides and provided at its curved sides with a pair of spirally located grooves I1 5 one end of the groove l'l starting at the lowermost point of the cup cavity It as indicated by the numeral "a and extending up the side walls of the cavity l6 spirally to the point Ilb adjacent the top of the cavity ll at which point the groove ll fades out into the surface plane'of the cavity l6 at that point. Below the cavity l6 of the cup l5 are located two annular grooves l8 and Ilia. On the inner periphery of the grooves l8 and 18a,

I have moulded in annular rings l9 and 20. The rings l9 and are further provided with contact pins 2| and 22 which are projected upwardly through the composition of the cup l5 into the lower ends of the groove Ila in the cup cavity l6 such that when the cup is at rest a ball of mer- 20 cury 23 will connect the pins 2| and 22 and thereby close an electrical circuit through stationary brush members 2 which are maintained in a stationary position with respect to rotation in their respective housings 25 solidly embedded in the 25 stationary outer casing 26 which is composed of insulating material such as moulded bakelite and surrounds the shaft l0 and the cup I5. The brush housings 25 are provided with an internal cavity in which is located brush springs 26 adapt- 30 ed to resiliently maintain contact between the brushes 24 and the contact rings l9 and 20.

One of the improvements of my present invention over the previous application aforesaid and to which I wish to refer is the design of the circuit contacts. In actual practice it has been found that where a mercury ball continually revolves around a contact shaft or similar device there develops a surface scale of insulation such that an electrical contact between the mercury and the shaft is imperfect and irregular at times particularly after the device has been used for a time. In my present device, I have obviated this condition by providing separate positive and negative contacts which are embedded through the surface of the mercury ball to its interior when such ball has come to rest thereby not having to depend on a purely surface contact of the mercury ball. It has also been found in practice that rotating objects such as shaft 10 are not always reliable as contacting mediums in the use of a single circuit where the rotating shaft is used as a ground.

In the above description of my invention I have shown in dotted lines an electrical circuit 21, an 5 electrical source of energy such as a battery 28, and a series connected incandescent lamp as as an illustration of one application of my switch. When the shaft ill is at rest, the ball of mercury 23 seeking its lowest level will be deposited in one of the ends of the groove I! as illustrated in Fig. 1, at such time the incandescent lamp 28 having an electrical circuit provided therethrough will be illuminated but when the shaft i0 is rotated the groove il oflers an obstruction against the rotation of the mercury on the surface I6 and because of this obstruction and the centrifugal force set up by the spinning of the cup and mercury ball together, the mercury ball is deflected upwardly in the cup and away from the contacts 2| therebyopening the circuit to the lamp 29.

If it be assumed that the shafting l3 and it represents the cable of a speedometer in a moving vehicle and the incandescent lamp 2| 9. stop light on the rear of the vehicle it will readily be apparent that when such vehicle is slowed down to a predetermined speed stop light 29 will automatically become illuminated. A simple switch 30 may be provided if desired to open the electrical circuit at any time when the vehicle is not in use.

It is to be understood that and it is readily apparent that, my switch is not limited in its use to a motor vehicle but could be used on stationary machinery or any other place where a warning signal might be desired to indicate a change of speed and it is also apparent that the contacting of the mercury may be regulated with respect to the speed of the rotating cup by designing the cup cavities with difierent degrees of pitch thereby varying the centrifugal force effect on the mercury ball with respect to its'outward movement such that a. slow speed of the shaft with a flat angle on the side would cause the ball of mercury to move outwardly while a steeper" aoaaesa mercury located in the cup cavity of said interj nal cup shaped rotor, a spiral groove located in the surface of said cavity, electrical contacts located in the bottom of said spiral groove and connecting with said rings, mercury located in said cavity adaptedto engage said contacts in said grooves when said rotor is at a rest position.

2. An improved electrical switch comprising a rotor, a cup-shaped cavity located in said rotor, electrical contact rings connecting said cavity in said rotor, a casing surrounding said rotor, electrical contact members attached to said casing adapted to engage said contact rings in said rotor. mercury located in the cavity of said rotor, guide members located on the internal surface of said cavity adapted to guide said mercury upward and outward by means of centrifugal force when said rotor is revolved.

3. In a centrifugal mercury operated switch,

a rotor having an internally disposed cup-shaped cavity adapted to maintain a small portion of mercury therein, a guide member located on the inner surfae of said cup-shaped cavity for the purpose of deflecting said mercury upward and outward when said rotor is rotated and to prevent the rotation of said cup-shaped cavity from surface slippage on said mercury, electrical contact members connected with the said cavity for the purpose of closing a circuit through said mercury when said rotor is at rest.

4. In a centrifugally operated mercury switch, a hollow rotor, a deflector member located on the inner surface of said hollow rotor adapted to displace a mercury ball by means of centrifugal force when said rotor is rotated, electrical contact means connecting said cavity of said rotor, and a stationary casing adapted to enclose said rotor and hold said contact members.

GUY S. MOORE. 

